Cool-tip thermocouple including two-piece hub

ABSTRACT

An ablation electrode system includes a handle assembly; a needle electrode assembly supported in and extending from the handle assembly. The needle electrode assembly includes an outer tube having at least a conductive distal tip and defining a cavity therein; and an inner tube disposed at least partially within the cavity of the outer tube and defining a lumen therein. The ablation electrode assembly includes a hub assembly fluidly connected to the needle electrode assembly. The hub assembly defines a first chamber and a second chamber; wherein the proximal end portion of the inner tube is in fluid communication with the first chamber and the proximal end portion of the outer tube is in fluid communication with the second chamber. The ablation electrode assembly includes a first fluid conduit fluidly connected to the first chamber; and a second fluid conduit fluidly connected to the second chamber.

BACKGROUND

1. Technical Field

The present disclosure relates to electrode thermosurgery systems and, more particularly, to cool-tip ablation electrode systems used for thermosurgery procedures and the like.

2. Background of Related Art

Therapeutic lesions in living bodies have been accomplished for many decades using radio-frequency (RF) and other forms of energy. The procedures have been particularly useful in the field of neurosurgery, typically where RF ablation needle electrodes (usually of elongated cylindrical geometry) are inserted into a living body. A typical form of such needle electrodes incorporates an insulated sheath from which an exposed (uninsulated) tip extends.

Generally, the ablation electrode is coupled between a grounded RF power source outside the body and a reference ground or indifferent electrode for contacting a large surface of the body. When an RF voltage is provided between the reference electrode and the inserted ablation electrode, RF current flows from the needle electrode through the body. Typically, the current density is very high near the tip of the needle electrode, which heats and destroys the adjacent tissue.

In the past, RF ablation electrode systems have incorporated temperature sensors, for example, in the form of a thermistor or thermocouple. In that regard, reference may be made to U.S. Pat. No. 4,411,266 to Cosman, the entire contents of which are incorporated herein by reference, for a detailed discussion of the same. Typically, the sensor is connected to a monitoring apparatus for indicating temperature to assist in accomplishing a desired lesion. As generally known, for a given tip geometry and tip temperature, lesions of a prescribed size can be made quite consistently.

A limitation of prior electrode ablation systems relates to the temperature of the tip. Specifically, prior needle electrodes of a given tip geometry never should effectively exceed a temperature of 100° C. At that temperature, the surrounding tissue will boil and char. Also, uncontrolled disruption, such as hemorrhage and explosive gas formation, may cause extremely hazardous and clinically dangerous effects on the patient. Consequently, the lesion size for a given electrode geometry generally has been considered to be somewhat limited by the fact that the tissue near the tip must not exceed 100° C.

Essentially, during RF ablation, the needle electrode temperature is highest near the tip, because the current density is the highest at that location. Accordingly, temperature falls off as a function of distance from the tip of the needle electrode, and except for possible abnormalities in tissue conductivity and so on, in a somewhat predictable and even calculable pattern. As an attendant consequence, the size of RF lesions for a given electrode geometry have been somewhat limited.

One proposed solution to the limitation of lesion's size has been to employ “off-axis” electrodes, for example the so called Zervas Hypophysectomy Electrode or the Gildenberg Side-Outlet electrode, as manufactured by Radionics, Inc., Burlington, Mass. However, such systems, in requiring multiple tissue punctures, increase the risk of hemorrhage, severely prolong the time of surgery and increase the level of delicacy. Also, an umbrella of off-axis lesions may not produce a desired homogenous or uniform lesion.

SUMMARY

The present disclosure relates to ablation electrode systems used for thermosurgery procedures and the like.

According to one aspect of the present disclosure, an ablation electrode system for use with a source of electrosurgical energy to ablate tissue in a living subject is provided. The ablation electrode system includes a handle assembly; and a needle electrode assembly supported in and extending from the handle assembly. The needle electrode assembly includes an outer tube having at least a conductive distal tip, a proximal end portion supported in the handle assembly, and defining a cavity therein; and an inner tube disposed at least partially within the cavity of the outer tube and having a proximal end portion supported within the handle assembly, the inner tube defining a lumen therein.

The ablation electrode system further includes a hub assembly supported within the handle assembly and fluidly connected to the needle electrode assembly. The hub assembly includes an outer shell defining a lumen therein; and an inner manifold operatively supported in the lumen of the outer shell. The inner manifold and the outer shell are configured and dimensioned so as to define a first chamber and a second chamber therebetween. The proximal end portion of the inner tube is in fluid communication with the first chamber and the proximal end portion of the outer tube is in fluid communication with the second chamber.

The ablation electrode system further includes an electrical conduit electrically connected to the outer tube of the needle electrode assembly; a first fluid conduit fluidly connected to the first chamber; and a second fluid conduit fluidly connected to the second chamber.

According to another aspect of the present disclosure, an ablation electrode system is provided and includes a handle assembly; a needle electrode assembly supported in and extending from the handle assembly. The needle electrode assembly includes an outer tube having at least a conductive distal tip, a proximal end portion supported in the handle assembly, and defining a cavity therein; and an inner tube disposed at least partially within the cavity of the outer tube and having a proximal end portion supported within the handle assembly, the inner tube defining a lumen therein.

The ablation electrode assembly includes a hub assembly supported within the handle assembly and fluidly connected to the needle electrode assembly. The hub assembly defines a first chamber and a second chamber; wherein the proximal end portion of the inner tube is in fluid communication with the first chamber and the proximal end portion of the outer tube is in fluid communication with the second chamber.

The ablation electrode assembly includes an electrical conduit electrically connected to the outer tube of the needle electrode assembly; a first fluid conduit fluidly connected to the first chamber; and a second fluid conduit fluidly connected to the second chamber.

According to yet another aspect of the present disclosure, an ablation system for ablating tissue in a living subject is provided. The ablation system includes an ablation electrode system including a needle electrode assembly. The needle electrode assembly includes an outer tube having at least a conductive distal tip and defining a cavity therein; and an inner tube disposed at least partially within the cavity of the outer tube and defining a lumen therein.

The ablation electrode system further includes a hub assembly fluidly connected to the needle electrode assembly. The hub assembly defines a first chamber and a second chamber; wherein a proximal end portion of the inner tube is in fluid communication with the first chamber and a proximal end portion of the outer tube is in fluid communication with the second chamber.

The ablation system includes a source of electrosurgical energy; a source of fluid; an electrical conduit electrically interconnecting the outer tube of the needle electrode assembly and the source of electrosurgical energy; a first fluid conduit fluidly interconnecting the source of fluid and the first chamber; and a second fluid conduit fluidly connected to the second chamber.

For a better understanding of the present invention and to show how it may be carried into effect, reference will be made by way of example to the accompanying drawings.

BRIEF DECRIPTION OF THE DRAWINGS

In the drawings, which constitute a part of the specification, exemplary embodiments exhibiting various objectives and features hereof are set forth, specifically:

FIG. 1 is a perspective view of an ablation electrode system in accordance with an embodiment of the present disclosure;

FIG. 2 is an enlarged perspective view of the ablation electrode system of FIG. 1, with a handle half-section removed therefrom and a hub assembly disposed therein shown partially broken away;

FIG. 3 is a longitudinal cross-sectional view of the ablation electrode system of FIGS. 1 and 2;

FIG. 4 is an enlarged longitudinal cross-sectional view of the hub assembly of FIGS. 2 and 3;

FIG. 5 is a longitudinal cross-sectional view of the outer shell of the hub assembly of FIGS. 2-4, including a needle electrode shown operative connected thereto;

FIG. 6 is a perspective view an inner manifold of the hub assembly of FIGS. 2-4;

FIG. 7 is a longitudinal cross-sectional view of the inner manifold of FIG. 6;

FIG. 8 is a perspective view of an ablation electrode system according to an alternate embodiment of the present disclosure;

FIG. 9 is a longitudinal cross-sectional view of the ablation electrode system of FIG. 8;

FIG. 10 is a longitudinal cross-sectional view of the outer shell of the hub assembly of FIG. 9, including needle electrodes shown operative connected thereto;

FIG. 10A is a distal end view of the outer shell of the hub assembly of the ablation electrode system of FIG. 8;

FIG. 11 is a perspective view an inner manifold of the hub assembly of FIG. 9;

FIG. 12 is a longitudinal cross-sectional view of the inner manifold of FIG. 11;

FIG. 13 is a perspective view of an ablation electrode system illustrating a strain relief member operatively associated therewith for support of the cables and/or conduits entering the handle;

FIG. 14 is a schematic perspective view of a strain relief member for use with ablation electrode system;

FIG. 15 is a schematic longitudinal cross-sectional view of another strain relief member shown supported in the handle of the ablation electrode system;

FIG. 16 is a schematic longitudinal cross-sectional view of yet another strain relief member shown supported in the handle of the ablation electrode system;

FIG. 17 is a schematic perspective view of another strain relief member for use with ablation electrode system; and

FIG. 18 is a cross-sectional view of the strain relief member of FIG. 17, as taken through 18-18 of FIG. 17.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of ablation electrode systems, in accordance with the present disclosure, will now be described in detail with reference to the drawings figures wherein like reference numerals identify similar or identical structural elements. As shown in the drawings and described throughout the following description, as is traditional when referring to relative positioning on a surgical instrument, device or apparatus, the term “proximal” refers to the end of the instrument, apparatus or device that is closer to the user and the term “distal” refers to the end of the apparatus that is further away from the user.

Referring initially to FIGS. 1-7, an electrode ablation system, according to an embodiment of the present disclosure, is generally designated as ablation system 100. Ablation system 100 includes a housing or handle assembly 110, and at least one needle electrode assembly 150 supported within and extending from housing assembly 110. Housing assembly 110 and needle electrode assembly 150 define a central longitudinal axis “X”.

As seen in FIGS. 1-3, housing assembly 110 includes a housing or handle 112 having first half-section 112 a and a second half-section 112 b selectively connectable to one another (e.g., in a snap-fit manner) via connecting structure 114 or the like. In one embodiment, housing 112 has a substantially conical shape defining a flattened proximal surface 116 a and a flattened distal surface 116 b (FIGS. 2 and 3). Housing 112 further includes an annular ramp-like structure 116 c extending from the surface thereof. Ramp-like structure 116 c acts as a surface against which an operators fingers contact for distal advancement of needle electrode 150 into the patient and/or proximal withdrawal of needle electrode 150 from the patient.

As seen in FIGS. 2-8, electrode ablation system 100 further includes a hub assembly 120 supported in housing 112 of housing assembly 110. Hub assembly includes a hub assembly outer shell 130 and a hub assembly inner manifold 140 disposed within outer shell 130. Outer shell 130 and inner manifold 140 of hub assembly are each fabricated from a suitable electrically non-conductive material.

As seen in FIGS. 2-5, hub assembly outer shell 130 includes a body portion 132 defining a central lumen 134 extending therethrough. Outer shell 130 defines a central longitudinal axis “X1” extending through central lumen 134. In an embodiment, when outer shell 130 is positioned in housing 112, the central longitudinal “X1” axis thereof at least substantially aligns with the central longitudinal “X” axis of housing 112 and needle electrode assembly 150. Central lumen 134 of outer shell 130 includes a tapered distal end 136 defining a constricted passage 134 a therethrough. Passage 134 a is sized to support and receive needle electrode assembly 150 therein.

Body portion 132 of outer shell 130 may include an annular flange 138 formed therearound. As seen in FIGS. 2 and 3, annular flange 138 of outer shell 130 is receiveable in a complementary annular channel or groove 118 formed or provided in housing 112. Accordingly, annular flange 138 and annular groove 118 cooperate to fix the location of hub assembly 120 relative to housing 112.

As seen in FIGS. 2-4, 6 and 7, inner manifold 140 is configured and dimensioned for support within lumen 134 of outer shell 130. Inner manifold 140 includes a body portion 142 defining a first or inflow lumen 144 a formed at least partially in a proximal end portion 142 b thereof. Inner manifold 140 further includes a second or outflow lumen 144 b extending entirely therethrough. Inner manifold 140 further includes a third lumen 144 c formed at least partially in a distal end portion 142 a thereof.

As seen in FIGS. 3, 4, 6 and 7, inner manifold 140 defines a first recess 148 formed therein such that when inner manifold 140 is inserted into lumen 134 of outer shell 130, first recess 148 defines a first cavity or chamber 122 between outer shell 130 and inner manifold 140. As seen in FIGS. 3 and 4, first lumen 144 a and third lumen 144 c are each in fluid communication with first chamber 122.

With continued reference to FIGS. 3 and 4, when inner manifold 140 is inserted into lumen 134 of outer shell 130, a second chamber 124 is defined in tapered distal end 136 of outer shell 130. When inner manifold 140 is so positioned, second lumen 144 b of manifold 140 is in fluid communication with the second chamber 124.

As seen in FIGS. 3, 4, 6 and 7, body portion 142 of inner manifold 140 may include an annular groove 142 a formed therein. As seen in FIGS. 3 and 4, annular groove 142 a of body portion 142 of inner manifold 140 is configured and dimensioned to receive a complementary annular flange or rib 128 formed in body portion 132 of outer shell 130. Accordingly, annular flange 128 and annular groove 142 c cooperate to fix the location of inner manifold 140 relative to outer shell 130.

In addition, as seen in FIG. 4, a glue “G”, including and not limited to, adhesives, epoxies, bonding agents, cements, silicones and the like, is applied in a proximal or rear portion of lumen 134 of outer shell 130, on a proximal or rear surface of inner manifold 140, and at locations therebetween. Glue “G” functions to further secure inner manifold 140 within outer shell 130 and to create a seal between outer shell 130 and inner manifold 140 to thereby inhibit and/or prevent the escape of fluid from therebetween.

In an embodiment, as seen in FIGS. 2-4, hub assembly 120 includes a seal element 126 (e.g., an O-ring) disposed between body portion 132 of outer shell 130 and body portion 142 of inner manifold 140. Seal element 126 functions to reduce and/or prevent fluid from traveling between first chamber 122 and second chamber 124.

As seen in FIGS. 1-4, a first or in-flow conduit 10 is fluidly connected to first lumen 144 a of inner manifold 140. A distal end of first conduit 10 extends through housing 112 of housing assembly 110 and is frictionally inserted into first lumen 144 a of inner manifold 140 of hub assembly 120.

With continued reference to FIGS. 1-4, a second or out-flow conduit 20 is fluidly connected to second lumen 144 b of inner manifold 140. Desirably, a distal end of second conduit 20 extends through housing 112 of housing assembly 110 and is frictionally inserted into second lumen 144 b of inner manifold 140 of hub assembly 120.

Turning now to FIGS. 1-5, needle electrode assembly 150 is described in greater detail. Needle electrode assembly 150 includes an outer tube 152 a having an exposed distal end portion 154 a terminating in a sharpened distal tip 156 a which is constructed so as to penetrate tissue with a minimum risk of hemorrhage from the puncture tract. Outer tube 152 a is constructed from a suitable electrically conductive material. Outer tube 152 a includes a proximal end portion 158 a supported in housing 112, and in an embodiment, in a distal lumen 134 b formed in and extending distally from constricted passage 134 a of outer shell 130, as seen in FIGS. 4 and 5. Outer tube 152 a is hollow and defines a cavity 160 a therein.

In an embodiment, the non-exposed part of outer tube 152 a may be surrounded by a suitable insulating material. The insulating material may be any material which is biologically acceptable and suitable for insertion into tissue. Since distal end portion 154 a is exposed or non-insulated, distal end portion 154 a is capable of DC or AC delivery, preferably RF delivery.

Needle electrode assembly 150 further includes an inner tube 152 b disposed substantially co-axially within cavity 160 a of outer tube 152 a. Inner tube 152 b includes a distal end portion 156 b (see FIGS. 6 and 7) located near distal end portion 154 a of outer tube 152 a and a proximal end portion 158 b extending from proximal end portion 158 a of outer tube 152 a. Proximal end portion 158 b of inner tube 152 b extends through constricted passage 134 a and into or through third lumen 144 c of inner manifold 140. It is envisioned that proximal end portion 158 b of inner tube 152 b is in fluid communication with first cavity or chamber 122 defined between inner manifold 140 and outer shell 130, see FIGS. 2-4.

In use, cooling fluid “F” is delivered to distal tip 156 a of outer tube 152 a from in-flow conduit 10. In particular, cooling fluid “F” travels from in-flow conduit 10, into first chamber 122, into lumen 160 b (see FIGS. 6 and 7) of inner tube 152 b of needle electrode assembly 150, to distal tip 156 a of outer tube 152 a. Cooling fluid “F” is led away from distal tip 156 a of outer tube 152 a through cavity 160 a, through second chamber 124, through second lumen 144 b of inner manifold 140, and out through out-flow tube 20. Cooling fluid “F” may be communicated to a collecting container (not shown) or back to a source of fluid “SF” (see FIG. 1) for re-circulation. Circulation of cooling fluid “F” may be established with the use of a suitable pump (not explicitly shown).

As seen in FIGS. 2, 3, 6 and 7, electrode ablation system 100 further includes a first electrical conduit 170 extending through housing 112 and electrically connected to outer tube 152 a of needle electrode assembly 150. In particular, first electrical conduit 170 includes a distal end 170 a electrically connected to outer tube 152 a at a location distal of hub assembly 120 and within housing 112. First electrical conduit 170 is also electrically connected to a source of electrosurgical energy “E”. Accordingly, electrosurgical energy may be delivered from the source of electrosurgical energy, through first electrical conduit 170, to outer tube 152 a.

As seen in FIGS. 2, 4, 6 and 7, electrode ablation system 100 further includes a thermocouple assembly 172 operatively associated with inner tube 152 b. Thermocouple assembly 172 includes a first wire or thermocouple 174 extending through lumen 160 b of inner tube 152 b. A distal end 174 a of first wire 174 is desirably electrically secured to distal end portion 156 b of inner tube 152 b, as by, for example, soldering and the like. First wire 174 may be fabricated from constantan (i.e., a high-resistance alloy of approximately 40% nickel and 60% copper). However, other suitable materials may be used for first wire 174, such as, for example, any suitable conductor that is dissimilar from inner tube 152 b (e.g., stainless steel) such that a thermocouple is created between the two materials.

Thermocouple assembly 172 further includes a second wire 176 having a distal end 176 a electrically connected to inner tube 152 b. In an embodiment, distal end 176 a of second wire 176 is connected to a proximal end portion 158 b of inner tube 152 b. Second wire 176 functions to electrically interconnect first wire 174 and a thermocouple measuring circuit. Accordingly, a temperature measurement signal from the thermocouple measuring circuit may then be sent to an electrosurgical energy source “E” and/or a central processing unit for monitoring.

As seen in FIGS. 1, 2 and 7, each of electrical conduit 170, first wire 174 and second wire 176 may be contained in a single cable 180.

Turning now to FIGS. 8-12, an electrode ablation system, in accordance with another embodiment of the present disclosure, is generally designated as 200. Electrode ablation system 200 is substantially similar to ablation system 100 and will be discussed in detail to the extent necessary to identify differences in construction and operation. Unlike electrode ablation system 100, which includes a single needle electrode assembly 150, electrode ablation system 200 includes three needle electrode assemblies 250 a-250 c extending distally from housing 112 of housing assembly 110. While a single and three needle electrode assemblies have been shown and described herein, any suitable number of needle electrode assemblies may be provided.

As seen in FIGS. 9-12, hub assembly 220 of electrode ablation system 200 includes a hub assembly outer shell 130 and a hub assembly inner manifold 240 operatively disposed within outer shell 230.

As seen in FIGS. 9, 10 and 10A, hub assembly outer shell 230 includes a body portion 232 defining a central lumen 234 extending therethrough. Desirably, outer shell 230 includes three constricted passages 236 a-236 c extending through a distal end portion 230 a of outer shell 230 and in fluid communication with central lumen 234. Desirably, each passage 236 a-236 c is sized to support and receive a proximal end of outer tube 252 a of a respective needle electrode assembly 250 a-250 c.

As seen in FIGS. 9, 11 and 12, inner manifold 240 is configured and dimensioned for support within lumen 234 of outer shell 230. Inner manifold 240 includes a body portion 242 defining a first or inflow lumen 244 a formed at least partially in a proximal end portion 242 b thereof. Inner manifold 240 further includes a second or outflow lumen 244 b extending entirely therethrough. Inner manifold 240 further includes a plurality of third lumens 244 c formed at least partially in a distal end portion thereof 242 a. Each third lumen 244 c of inner manifold 240 is configured and dimensioned to receive and support a proximal end of a respective inner tube 252 b of needle electrode assemblies 250 a-250 c therein.

As seen in FIGS. 9, 11 and 12, inner manifold 240 defines a first recess 248 formed therein such that when inner manifold 240 is inserted into lumen 234 of outer shell 230, first recess 248 defines a first cavity or chamber 222 between outer shell 230 and inner manifold 240. As can be appreciated and similar to hub assembly 120 of electrode ablation system 100, first lumen 244 a and each third lumen 244 c are in fluid communication with first chamber 222.

With continued reference to FIGS. 9, 11 and 12, when inner manifold 240 is inserted into lumen 234 of outer shell 230, a second chamber 224 is defined in distal end portion 236 of lumen 234 of outer shell 230. When inner manifold 240 is so positioned, second lumen 244 b of manifold 240 is in fluid communication with the second chamber 224.

As seen in FIGS. 9-12, each needle electrode assembly 250 a-250 c of electrode ablation system 200 is substantially similar to needle electrode assembly 150 of electrode ablation system 100, and therefore reference may be made to the detailed discussion of needle electrode assembly 150 for an understanding and description of needle electrode assemblies 250 a-250 c.

Use of electrode ablation system 200 will now be described in detail. In use, cooling fluid “F” is delivered to a distal tip 256 of each outer tube 252 a. In particular, cooling fluid travels from in-flow conduit 10, into first chamber 222, into a lumen of an inner tube (see FIGS. 6 and 7) of each needle electrode assembly 250 a-250 c, to a distal tip 256 of the outer tube of each needle electrode assembly 250 a-250 c. The cooling fluid is led away from distal tip 256 of the outer tube of each needle electrode assembly 250 a-250 c, through second chamber 224, through second lumen 244 b of inner manifold 240, and out through out-flow tube 20.

As seen in FIGS. 11 and 12, a first wire 174 of thermocouple assembly 172 extends through lumen 160 b (see FIG. 6) of at least one inner tube 252 b of needle electrode assemblies 250 a-250 c. As mentioned above, a distal end 174 a of first wire 174 is desirably electrically secured to a distal end portion of inner tube 252 b, as by, for example, soldering and the like. Desirably, first wire 174 is fabricated from constantan or the like (i.e., a high-resistance alloy of approximately 40% nickel and 60% copper). A second wire 176 of thermocouple assembly 172 has a distal end electrically connected to inner tube 252 b.

The handle of needle electrode system 200 is configured and adapted so as to maintain needle electrode assemblies 250 a-250 c substantially parallel to one another during insertion and/or placement of needle electrode assemblies 250 a-250 c into a target surgical site.

Turning now to FIGS. 13-18, electrode ablation systems 100, 200 may each include an adjustable cord strain relief member 50 operatively disposed on cable 180, in-flow conduit 10, and/or out-flow conduit 20. Strain relief member 50 is configured and dimensioned for operative engagement in an aperture 114 (see FIGS. 1 and 2) of housing 112 of handle assembly 110. In an embodiment, aperture 114 is formed in a side of housing 112 of handle assembly 110 such that cable 180, in-flow conduit 10 and/or out-flow conduit 20 may extend out of the side thereof. By having cable 180, in-flow conduit 10 and/or out-flow conduit 20 exit from a side of housing 112 of handle assembly 110 a strain relief for cable 180, in-flow conduit 10 and/or out-flow conduit 20 is established.

Strain relief member 50 includes a body portion 52 having a substantially hour-glass configuration. Body portion 52 may include a first substantially spherical portion 52 a and a second substantially spherical portion 52 b. Desirably, second portion 52 b of body portion 52 is poly-axially supported (e.g., in the manner of a ball and socket joint) within a complementarily sized and shaped aperture 114.

As seen in FIGS. 14-16, an annular rib 54 a may be provided on the surface of second body portion 52 a for engaging the inner surface of shaped aperture 114. Strain relief member 50 may also be provided with a shield or apron 56 extending radially therefrom. Shield 56 may be disposed within an appropriately sized recess 116 formed in handle 112, as seen in FIG. 15, or may be disposed externally of handle 112, as seen in FIG. 16.

As seen in FIGS. 17 and 18, strain relief member 50 may include means for locking including a tapered portion 52 c disposed between first body portion 52 a and second body portion 52 b, and at least one longitudinally oriented locking rib 54 b projecting from tapered portion 52 c. Locking rib 54 b is configured and dimensioned to selectively engage complementary channels 118 formed in handle 112. In use, as strain relief member 50 is moved in a first direction (as indicated by arrow “A”), locking rib 54 b disengages channels 118 to unlock strain relief member 50, and as strain relief member 50 is moved in a second direction (opposite to direction “A”), locking rib 54 b engages channels 118 to lock strain relief member 50.

The foregoing description is merely a disclosure of particular embodiments and is no way intended to limit the scope of the invention. Other possible modifications are apparent to those skilled in the art and all modifications are to be defined by the following claims. 

1. An ablation electrode system for use with a source of electrosurgical energy to ablate tissue in a living subject, the ablation electrode system comprising: a handle assembly; a needle electrode assembly supported in and extending from the handle assembly, the needle electrode assembly including: an outer tube having at least a conductive distal tip, a proximal end portion supported in the handle assembly, and defining a cavity therein; and an inner tube disposed at least partially within the cavity of the outer tube and having a proximal end portion supported within the handle assembly, the inner tube defining a lumen therein; a hub assembly supported within the handle assembly and fluidly connected to the needle electrode assembly, the hub assembly including: an outer shell defining a lumen therein; and an inner manifold operatively supported in the lumen of the outer shell, the inner manifold and the outer shell being configured and dimensioned so as to define a first chamber and a second chamber therebetween; wherein the proximal end portion of the inner tube is in fluid communication with the first chamber and the proximal end portion of the outer tube is in fluid communication with the second chamber; an electrical conduit electrically connected to the outer tube of the needle electrode assembly; a first fluid conduit fluidly connected to the first chamber; and a second fluid conduit fluidly connected to the second chamber.
 2. The ablation electrode assembly according to claim 1, wherein the outer tube of the needle electrode assembly is fabricated from an electrically conductive material.
 3. The ablation electrode assembly according to claim 2, wherein a layer of insulative material is disposed on an outer surface of the outer tube and wherein the distal tip of the outer tip is exposed.
 4. The ablation electrode assembly according to claim 3, wherein the inner tube delivers fluid to the distal tip of the outer tube.
 5. The ablation electrode assembly according to claim 4, further comprising a thermocouple assembly electrically connected to the inner tube.
 6. The ablation electrode assembly according to claim 5, wherein the thermocouple assembly includes a constantan wire extending through the lumen of the inner tube and electrically connected to a distal end of the inner tube.
 7. The ablation electrode assembly according to claim 6, wherein the inner manifold defines a lumen therein interconnecting the second chamber of the hub assembly to the second fluid conduit.
 8. The ablation electrode assembly according to claim 7, wherein an adhesive is applied to a proximal end of the inner manifold and the outer shell to at least one to secure the inner manifold within the outer shell and to seal the hub assembly from fluid leaks from between the outer shell and the inner manifold.
 9. The ablation electrode assembly according to claim 7, wherein a seal element is provided between the outer shell and the inner manifold of the hub assembly to prevent transmission of fluid between the first chamber and the second chamber.
 10. The ablation electrode assembly according to claim 7, further comprising a plurality of needle electrode assemblies are supported in and extend from the handle assembly, wherein a proximal end portion of each inner tube is in fluid communication with the first chamber and a proximal end portion of each outer tube is in fluid communication with the second chamber.
 11. The ablation electrode assembly according to claim 10, wherein the thermocouple assembly includes a constantan wire extending through the lumen of at least one inner tube and electrically connected to a distal end of said at least one inner tube.
 12. The ablation electrode assembly according to claim 1, wherein at least one of the electrical conduit, the first fluid conduit, and the second fluid conduit exit from a side of the handle assembly.
 13. An ablation electrode system for use with a source of electrosurgical energy to ablate tissue in a living subject, the ablation electrode system comprising: a handle assembly; a needle electrode assembly supported in and extending from the handle assembly, the needle electrode assembly including: an outer tube having at least a conductive distal tip, a proximal end portion supported in the handle assembly, and defining a cavity therein; and an inner tube disposed at least partially within the cavity of the outer tube and having a proximal end portion supported within the handle assembly, the inner tube defining a lumen therein; a hub assembly supported within the handle assembly and fluidly connected to the needle electrode assembly, the hub assembly defining a first chamber and a second chamber; wherein the proximal end portion of the inner tube is in fluid communication with the first chamber and the proximal end portion of the outer tube is in fluid communication with the second chamber; an electrical conduit electrically connected to the outer tube of the needle electrode assembly; a first fluid conduit fluidly connected to the first chamber; and a second fluid conduit fluidly connected to the second chamber.
 14. The ablation electrode assembly according to claim 13, wherein the outer tube of the needle electrode assembly is fabricated from an electrically conductive material.
 15. The ablation electrode assembly according to claim 14, wherein a layer of insulative material is disposed on an outer surface of the outer tube and wherein the distal tip of the outer tip is exposed.
 16. The ablation electrode assembly according to claim 15, wherein the inner tube delivers fluid to the distal tip of the outer tube.
 17. The ablation electrode assembly according to claim 16, further comprising a thermocouple assembly electrically connected to the inner tube.
 18. The ablation electrode assembly according to claim 17, wherein the thermocouple assembly includes a constantan wire extending through the lumen of the inner tube and electrically connected to a distal end of the inner tube.
 19. The ablation electrode assembly according to claim 18, wherein the inner manifold defines a lumen therein interconnecting the second chamber of the hub assembly to the second fluid conduit.
 20. The ablation electrode assembly according to claim 19, wherein the hub assembly includes an outer shell defining a lumen therein and an inner manifold operatively supported in the lumen of the outer shell.
 21. The ablation electrode assembly according to claim 20, wherein an adhesive is applied to a proximal end of the inner manifold and the outer shell to at least one of secure the inner manifold within the outer shell and seal the hub assembly from fluid leaks from between the outer shell and the inner manifold.
 22. The ablation electrode assembly according to claim 20, wherein a seal element is provided between the outer shell and the inner manifold of the hub assembly to prevent transmission of fluid between the first chamber and the second chamber.
 23. The ablation electrode assembly according to claim 20, further comprising a plurality of needle electrode assemblies are supported in and extend from the handle assembly, wherein a proximal end portion of each inner tube is in fluid communication with the first chamber and a proximal end portion of each outer tube is in fluid communication with the second chamber.
 24. The ablation electrode assembly according to claim 23, wherein the thermocouple assembly includes a constantan wire extending through the lumen of at least one inner tube and electrically connected to a distal end of said at least one inner tube.
 25. The ablation electrode assembly according to claim 13, wherein at least one of the electrical conduit, the first fluid conduit, and the second fluid conduit exit from a side of the handle assembly.
 26. An ablation system for ablating tissue in a living subject, the ablation system comprising: an ablation electrode system comprising: a needle electrode assembly including: an outer tube having at least a conductive distal tip and defining a cavity therein; and an inner tube disposed at least partially within the cavity of the outer tube and defining a lumen therein; a hub assembly fluidly connected to the needle electrode assembly, the hub assembly defining a first chamber and a second chamber; wherein a proximal end portion of the inner tube is in fluid communication with the first chamber and a proximal end portion of the outer tube is in fluid communication with the second chamber; a source of electrosurgical energy; a source of fluid; an electrical conduit electrically interconnecting the outer tube of the needle electrode assembly and the source of electrosurgical energy; a first fluid conduit fluidly interconnecting the source of fluid and the first chamber; and a second fluid conduit fluidly connected to the second chamber. 